Argon addition to remote plasma oxidation

ABSTRACT

Methods for conformal radical oxidation of structures are provided. The method comprises positioning a substrate in a processing region of a processing chamber. The method further comprises flowing hydrogen gas into a precursor activator at a first flow rate, wherein the precursor activator is fluidly coupled with the processing region. The method further comprises flowing oxygen gas into the precursor activator at a second flow rate. The method further comprises flowing argon gas into the precursor activator at a third flow rate. The method further comprises generating a plasma in the precursor activator from the hydrogen gas, oxygen gas, and argon gas. The method further comprises flowing the plasma into the processing region. The method further comprises exposing the substrate to the plasma to form an oxide film on the substrate, wherein a growth rate of the oxide film is controlled by adjusting the third flow rate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 16/226,862, filed Dec. 20, 2018, which claims benefit of U.S.provisional patent application Ser. No. 62/617,387, filed Jan. 15, 2018,both of which are incorporated herein by reference in their entirety.

BACKGROUND Field

Implementations of the present disclosure generally relate tosemiconductor device fabrication and in particular to methods forconformal radical oxidation of structures such as high aspect ratiostructures.

Description of the Related Art

The production of silicon integrated circuits has placed difficultdemands on fabrication processes to increase the number of devices whiledecreasing the minimum feature sizes on a chip. These demands haveextended to fabrication processes including depositing layers ofdifferent materials onto difficult topologies and etching furtherfeatures within those layers. Manufacturing processes for nextgeneration NAND flash memory involve especially challenging devicegeometries and scales. NAND is a type of non-volatile storage technologythat does not have need of power to retain data. To increase memorycapacity within the same physical space, a three-dimensional NAND (3DNAND) design has been developed. Such a design typically introducesalternating oxide layers and nitride layers, which are deposited on asubstrate. The alternating oxide layers and nitride layers are thenetched producing a structure having one or more surfaces extendingsubstantially perpendicular to the substrate. Such design considerationshave moved the field from oxidation of relatively low aspect ratiostructures, for example 10:1 aspect ratios, to high aspect ratio (HAR)structures, for example 40:1 or greater aspect ratios. Prior fabricationprocesses have included methods for filing gaps and trenches in HARstructures.

3D NAND flash structures are often coated with silicon nitride(Si_(x)N_(y)) layers, for example, Si₃N₄, that are to be oxidizedconformally in HAR structures. 3D NAND flash structures may have high orultra-high aspect ratios, for example, a 40:1 aspect ratio, between a40:1 and a 100:1 aspect ratio, a 100:1 aspect ratio, or even greaterthan 100:1 aspect ratio. New fabrication processes are looked-for forconformal deposition of layers on the faces of HAR structures, ratherthan simply filling gaps and trenches. For example, forming layersconformally onto the face of a HAR structure may involve slowerdeposition rates. “Conformally” generally refers to uniform and/orconstant-thickness layers on faces of structures. In the context of HARstructures, “conformally” may be most relevant when discussing thethickness of oxidation on the structure faces that are substantiallyperpendicular to the substrate. A more conformal deposition can reducematerial build up at the top of the structure. Such material build upmay result in material prematurely sealing off the top of the trenchbetween adjacent structures, forming a void in the trench.Unfortunately, slowing the deposition rate also means increasing thedeposition time, which reduces processing efficiency and productionrates.

Thus, there is a need for improved processes for conformal oxidation ofhigh aspect ratio structures.

SUMMARY

Implementations of the present disclosure generally relate tosemiconductor device fabrication and in particular to methods forconformal radical oxidation of structures such as high aspect ratiostructures. In one implementation, a method for oxidation is provided.The method comprises flowing hydrogen gas into a processing region of aprocessing chamber at a first flow rate, wherein the processing regionhas a substrate positioned therein. The method further comprises flowingoxygen gas into a precursor activator at a second flow rate. The methodfurther comprises flowing argon gas into the precursor activator at athird flow rate. The method further comprises generating a plasma in theprecursor activator from the oxygen gas and argon gas. The methodfurther comprises flowing the plasma into the processing region wherethe plasma mixes with the hydrogen gas to create an activated processinggas. The method further comprises exposing the substrate to theactivated gas to form an oxide film on the substrate, wherein a growthrate of the oxide film is controlled by adjusting the third flow rate.

In another implementation, a method for oxidation is provided. Themethod comprises positioning a substrate in a processing region of aprocessing chamber. The method further comprises flowing hydrogen gasinto a precursor activator at a first flow rate, wherein the precursoractivator is fluidly coupled with the processing region. The methodfurther comprises flowing oxygen gas into the precursor activator at asecond flow rate. The method further comprises flowing argon gas intothe precursor activator at a third flow rate. The method furthercomprises generating a plasma in the precursor activator from thehydrogen gas, oxygen gas, and argon gas. The method further comprisesflowing the plasma into the processing region. The method furthercomprises exposing the substrate to the plasma to form an oxide film onthe substrate, wherein a growth rate of the oxide film is controlled byadjusting the third flow rate.

In yet another implementation, a method for oxidation is provided. Themethod comprises positioning a substrate in a processing region of aprocessing chamber. The method further comprises flowing hydrogen gasinto a precursor activator at a first flow rate, wherein the precursoractivator is fluidly coupled with the processing region. The methodfurther comprises flowing oxygen gas into the precursor activator andinto the processing region at a second flow rate. The method furthercomprises flowing argon gas into the precursor activator and into theprocessing region at a third flow rate. The method further comprisesgenerating a plasma in the precursor activator from the hydrogen gas,oxygen gas, and argon gas. The method further comprises flowing theplasma into the processing region. The method further comprises exposingthe substrate to the plasma to form an oxide film on the substrate,wherein a growth rate of the oxide film is controlled by adjusting thethird flow rate.

In yet another implementation, a method for oxidation is provided. Themethod comprises flowing hydrogen gas into a processing region of aprocessing chamber at a first flow rate, wherein the processing regionhas a substrate positioned therein. The method further comprises flowinghydrogen gas into a precursor activator at a second flow rate, whereinthe precursor activator is fluidly coupled with the processing region.The method further comprises flowing oxygen gas into the precursoractivator and into the processing region at a third flow rate. Themethod further comprises flowing argon gas into the precursor activatorand into the processing region at a fourth flow rate. The method furthercomprises generating a plasma in the precursor activator from thehydrogen gas, oxygen gas, and argon gas. The method further comprisesflowing the plasma into the processing region where the plasma mixeswith the hydrogen gas to create an activated processing gas. The methodfurther comprises flowing the plasma into the processing region.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe implementations, briefly summarized above, may be had by referenceto implementations, some of which are illustrated in the appendeddrawings. It is to be noted, however, that the appended drawingsillustrate only typical implementations of this disclosure and aretherefore not to be considered limiting of its scope, for the disclosuremay admit to other equally effective implementations.

FIG. 1 is a cross-sectional view of a remote plasma system according toone or more implementations of the present disclosure;

FIG. 2 is a process flow diagram of a method of selective oxidationaccording to one or more implementations of the present disclosure;

FIG. 3A depicts a cross-sectional view of a film structure having a highaspect ratio feature that may be processed according to one or moreimplementations of the present disclosure;

FIG. 3B depicts a cross-sectional view of the film structure of FIG. 3Ahaving a conformal oxide layer formed according to one or moreimplementations of the present disclosure;

FIG. 4 is a graph depicting growth rate and center to edge uniformity ofan oxide film formed according to implementations described herein;

FIG. 5 is a graph depicting oxide conformality based on the percent ofhydrogen gas and the presence or absence of argon; and

FIG. 6 is a graph depicting oxide quality based on the percent ofhydrogen gas relative to the percent of argon gas.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneimplementation may be beneficially incorporated in other implementationswithout further recitation.

DETAILED DESCRIPTION

The following disclosure describes methods for oxidizing silicon films.Certain details are set forth in the following description and in FIGS.1-6 to provide a thorough understanding of various implementations ofthe disclosure. Other details describing well-known structures andsystems often associated with remote plasma oxidation are not set forthin the following disclosure to avoid unnecessarily obscuring thedescription of the various implementations.

Many of the details, dimensions, angles and other features shown in theFigures are merely illustrative of particular implementations.Accordingly, other implementations can have other details, components,dimensions, angles and features without departing from the spirit orscope of the present disclosure. In addition, further implementations ofthe disclosure can be practiced without several of the details describedbelow.

Implementations described herein will be described below in reference toa remote plasma oxidation process. The apparatus description describedherein is illustrative and should not be construed or interpreted aslimiting the scope of the implementations described herein. Other toolscapable of performing remote plasma oxidation processes may also beadapted to benefit from the implementations described herein.

As the aspect ratio of HAR structures continues to increase, it becomesincreasingly difficult to grow conformal films within these HARstructures. For example, oxide films formed in HAR structures bycurrently available remote plasma oxidation processes have insufficientconformality for HAR structures as well as high pattern loading (e.g.,non-uniformity on patterned wafers compared to bare silicon wafers). Ithas been found by the inventors that argon addition during someimplementations of remote plasma oxidation can improve conformaloxidation growth while improving pattern loading. Not to be bound bytheory but it is believed that the addition of argon gas reduces therecombination of oxygen radicals, which increases the concentration ofoxygen radicals available for the plasma oxidation process. Thus, argongas can be used to control the growth rate of an oxide film. Forexample, an increase in the flow of argon gas will typically yield anincrease in the growth rate of the oxide film, whereas a decrease in theflow of argon gas will typically yield a decrease in the growth rate ofthe oxide film. In addition, argon addition improves strike reliabilityas argon has lower ionization energy and thus leads to easier plasmaformation.

The methods described herein may be performed using a plasma source, forexample a remote plasma source (RPS), and a processing chamber designedto perform atomic oxygen radical (O) growth (e.g., conformal radicaloxidation) in high aspect ratio (HAR) structures, for example trenchcapacitor dielectrics, gate dielectrics, and 3D NAND flash structures.In some implementations, the plasma source utilizes a gas mixture ofargon, oxygen and optionally hydrogen to initiate radical oxidation of asilicon-containing material, such as a silicon nitride (Si_(x)N_(y))material, for example Si₃N₄. In some implementations, the gas mixture ofargon, oxygen, and optionally hydrogen has a concentration of argon inthe range of about 5% to about 80%, for example, in the range of about10% to about 50%. In some implementations, the plasma initiates areaction to form silicon oxynitride (SiO_(x)N_(y)), for example, Si₂N₂O,as an intermediary to forming silica (SiO₂).

In some implementations, combinations of argon, hydrogen, and oxygen ina precursor activator, in some cases with post activator hydrogeninjection, during high temperature processing (for example, ˜500 to 1100degrees Celsius) delivers highly conformal oxidation growth of films(e.g. amorphous silicon, polysilicon, or silicon nitride) in very highaspect ratio structures (for example, a 40:1 aspect ratio, between a40:1 and a 100:1 aspect ratio, a 100:1 aspect ratio, or even greaterthan 100:1 aspect ratio.)

In some implementations, combinations of argon, hydrogen, and oxygen ina precursor activator, in some cases with post activator hydrogeninjection, during high temperature processing (for example, 500 to 1100degrees Celsius) delivers improved oxide quality and/or preventsdegraded quality.

FIG. 1 illustrates a substrate processing system 100 that may be used toperform the methods described herein. Other deposition chambers may alsobenefit from the present disclosure and the parameters disclosed hereinmay vary according to the particular deposition chamber used to form theHAR structures described herein. For example, other deposition chambersmay have a larger or smaller volume, requiring gas flow rates that arelarger or smaller than the gas flow rates recited for depositionchambers available from Applied Materials, Inc.

The substrate processing system 100 includes a thermal processingchamber 102 and a precursor activator 180 that couples to the thermalprocessing chamber 102 and is used to remotely provide radicals of aplasma to the processing region 113 of the thermal processing chamber102. The precursor activator 180 can also be used to provide anactivated gas mixture that is not a plasma, for example by applyingenergy to a gas that does not significantly ionize the gas. The thermalprocessing chamber 102 has a processing region 113 enclosed by one ormore sidewall(s) 114 (e.g., four sidewalls) and a base 115. The upperportion of sidewall 114 may be sealed to a window assembly 117 (e.g.,using “O” rings). A radiant energy assembly 118 is positioned over andcoupled to window assembly 117. The radiant energy assembly 118 has aplurality of lamps 119, which may be tungsten halogen lamps, eachmounted into a receptacle 121 and positioned to emit electromagneticradiation into the processing region 113. The window assembly 117 ofFIG. 1 has a plurality of light pipes 141, but the window assembly 117may just have a flat, solid window with no light pipes. The windowassembly 117 has an outer wall 116 (e.g., a cylindrical outer wall) thatforms a rim enclosing the window assembly 117 around a circumferencethereof. The window assembly 117 also has a first window 120 covering afirst end of the plurality of light pipes 141 and a second window 122covering a second end of the plurality of light pipes 141, opposite thefirst end. The first window 120 and second window 122 extend to, andengage with, the outer wall 116 of the window assembly 117 to encloseand seal the interior of the window assembly 117, which includes theplurality of light pipes 141. In such cases, when light pipes are used,a vacuum can be produced in the plurality of light pipes 141 by applyingvacuum through a conduit 153 through the outer wall 116 to one of theplurality of light pipes 141, which is in turn fluidly connected to therest of the pipes.

A substrate 101 is supported in the thermal processing chamber 102 by asupport ring 162 within the processing region 113. The support ring 162is mounted on a rotatable cylinder 163. By rotating the rotatablecylinder 163, the support ring 162 and substrate 101 are caused torotate during processing. The base 115 of the thermal processing chamber102 has a reflective surface 111 for reflecting energy onto the backsideof the substrate 101 during processing. Alternatively, a separatereflector (not shown) can be positioned between the base 115 of thethermal processing chamber 102 and the support ring 162. The thermalprocessing chamber 102 may include a plurality of temperature probes 171disposed through the base 115 of the thermal processing chamber 102 todetect the temperature of the substrate 101. In the event a separatereflector is used, as described above, the temperature probes 171 arealso disposed through the separate reflector for optical access toelectromagnetic radiation coming from the substrate 101.

The rotatable cylinder 163 is supported by a magnetic rotor 164, whichis a cylindrical member having a ledge 165 on which the rotatablecylinder 163 rests when both members are installed in the thermalprocessing chamber 102. The magnetic rotor 164 has a plurality ofmagnets in a magnet region 166 below the ledge 165. The magnetic rotor164 is disposed in an annular well 160 located at a peripheral region ofthe thermal processing chamber 102 along the base 115. A cover 173 restson a peripheral portion of the base 115 and extends over the annularwell 160 toward the rotatable cylinder 163 and support ring 162, leavinga tolerance gap between the cover 173 and the rotatable cylinder 163and/or the support ring 162. The cover 173 generally protects themagnetic rotor 164 from exposure to process conditions in the processingregion 113.

The magnetic rotor 164 is rotated by magnetic energy from a magneticstator 167 disposed around the base 115. The magnetic stator 167 has aplurality of electromagnets 168 that, during processing of the substrate101, are powered according to a rotating pattern to form a rotatingmagnetic field that provides magnetic energy to rotate the magneticrotor 164. The magnetic stator 167 is coupled to a linear actuator 169,which in this case is a screw drive, by a support 170. Operating thelinear actuator 169 moves the magnetic stator 167 along an axis 172 ofthe thermal processing chamber 102, which in turn moves the magneticrotor 164, the rotatable cylinder 163, the support ring 162, and thesubstrate 101 along the axis 172.

Processing gas is provided to the thermal processing chamber 102 througha chamber inlet 175, and exhausts through a chamber outlet oriented outof the page and generally along the same plane as the chamber inlet 175and the support ring 162 (not shown in FIG. 1). Substrates enter andexit the thermal processing chamber 102 through an access port 174formed in the sidewall 114 and shown at the rear in FIG. 1. Thesubstrate transportation process is not described herein.

The precursor activator 180 has a body 182 surrounding an interior space184 where a plasma 183 of ions, radicals, and electrons can be formed. Aliner 185 made of quartz or sapphire protects the body 182 from chemicalattack by the plasma. The interior space 184 preferably does not haveany electrical potential gradient present that might attract chargedparticles, e.g., ions. A gas inlet 186 is disposed at a first end 187 ofthe body 182 and opposite from a gas outlet 188 that is located at asecond end 189 of the body 182. When the precursor activator 180 iscoupled to the thermal processing chamber 102, the gas outlet 188 is influid communication with the thermal processing chamber 102 through adelivery line 190 to chamber inlet 175, such that radicals of the plasma183 generated within the interior space 184 are supplied to theprocessing region 113 of the thermal processing chamber 102. The gasoutlet 188 may have a diameter larger than the gas inlet 186 to allowthe excited radicals to be efficiently discharged at a targeted flowrate, and to minimize the contact between the radicals and the liner185. If targeted, a separate orifice may be inserted within the liner185 at the gas outlet 188 to reduce an inner dimension of the interiorspace 184 at the gas outlet 188. The diameter of the gas outlet 188 (ororifice, if used) can be selected to provide a pressure differentialbetween the processing region 113 and the precursor activator 180. Thepressure differential may be selected to yield a composition of ions,radicals, and molecules flowing in to the thermal processing chamber 102that is suitable to processes being performed in the thermal processingchamber 102.

To provide gas for plasma processing, a first gas source 192 is coupledto the gas inlet 186 via a first input of a four-way valve 194 and avalve 197 used to control the flow rate of gas released from the firstgas source 192. A second input of the four-way valve 194 may be coupledto a second gas source 198. A third input of the four-way valve may becoupled to a third gas source 199. Each of the first gas source 192, thesecond gas source 198, and the third gas source 199 may be, or include,one or more of a nitrogen-containing gas, an oxygen-containing gas, asilicon-containing gas, a hydrogen-containing gas, or a plasma forminggas such as argon or helium. A flow controller 196 is connected to thefour-way valve 194 to switch the valve between its different positions,depending upon which process is to be carried out. The flow controller196 also controls switching of the four-way valve 194.

The precursor activator 180 may be coupled to an energy source (notshown) to provide an excitation energy, such as an energy having amicrowave or RF frequency, to the precursor activator 180 to activatethe process gas traveling from the first gas source 192 into the plasma183. In the case where nitrogen-containing gas, for example, N₂, isused, the plasma activation in precursor activator 180 produces N*radicals, positively charged ions such as N⁺ and N₂ ⁺, and electrons inthe interior space 184. By locating the precursor activator 180 remotelyfrom the processing region 113 of thermal processing chamber 102,exposure of the substrate to ions can be minimized. Ions can damagesensitive structures on a semiconductor substrate, whereas radicals arereactive and can be used to perform beneficial chemical reactions. Useof an activated gas source such as the precursor activator 180 promotesexposure of the substrate 101 to radicals and minimizes exposure of thesubstrate 101 to ions.

In some implementations, a second hydrogen gas source (not shown) isfluidly coupled with the thermal processing chamber 102. The secondhydrogen gas source delivers hydrogen gas to the processing region 113where the hydrogen gas is activated by the remote plasma comprisingoxygen and argon delivered from the precursor activator 180 to theprocessing region 113. In some implementations where a high percentageof hydrogen gas is targeted, hydrogen gas may be supplied to theprocessing region 113 through both the third gas source 199 and thesecond hydrogen gas source.

In some implementations, a second argon gas source (not shown) iscoupled with the thermal processing chamber 102. The second argon gassource delivers argon gas to the processing region 113 where the argongas is activated by the remote plasma delivered from the precursoractivator 180 to the processing region 113. In some implementationswhere a high percentage of argon gas is targeted, argon gas may besupplied to the processing region 113 through both the second gas source198 and the second argon gas source.

FIG. 2 is a process flow diagram of a method 200 of oxidation accordingto one or more implementations of the present disclosure. The method 200may be used to oxidize films, such as, for example, amorphous siliconfilms, polysilicon films, silicon nitride films, alumina films, siliconoxide films, and the like. FIG. 3A depicts a cross-sectional view of afilm structure having a high aspect ratio feature that may be processedaccording to the method 200. FIG. 3B depicts a cross-sectional view ofthe film structure of FIG. 3A having a conformal oxide layer formedaccording to the method 200. Although the method 200 is described belowwith reference to a high aspect ratio structure that may be formed on afilm stack utilized to manufacture stair-like structures in the filmstack for three dimensional semiconductor devices, the method 200 mayalso be used to advantage in other device manufacturing applications.For example, the method 200 may also be used to advantage for DRAM(e.g., recessed channel array transistor “RCAT”). Further, it shouldalso be understood that the operations depicted in FIG. 2 may beperformed simultaneously and/or in a different order than the orderdepicted in FIG. 2. Additionally, the method 200 may be used toadvantage for selective oxidation and non-selective oxidation of films.

The method 200 begins at operation 210 by positioning a substrate into aprocess chamber, such as the thermal processing chamber 102 depicted inFIG. 1. The substrate may be the substrate 302 having a film structure300 formed thereon, or any subset of the film structure 300. Thesubstrate 302 without a film structure (i.e. just the substrate 302) mayalso be processed according to the method 200. The film structure 300may have a high aspect ratio feature 340 formed therein. The faces thatdefine the high aspect ratio feature 340 here are substantiallyperpendicular to the substrate 302, but other types of features havingtapered, angled, slanted, or curved faces can be processed using themethod 200. Note that the high aspect ratio feature 340 provides accessto the faces of the HAR structures, for example for gas transmissionand/or reactant removal. As aspect ratio increases, the surface area ofthe HAR structures and the depth of the features likewise increase. Asaspect ratio increases, conformal radical oxidation of the faces of theHAR structures is increasingly hampered by oxygen radical depletion,especially near the bottom of the high aspect ratio feature 340. Thisoxygen radical depletion leads to an increase in incubation time and acorresponding decrease in growth rate of the conformal oxide film. Asdisclosed herein, argon addition to the radical plasma oxidation processreduces oxygen recombination near the bottom of the high aspect ratiofeature 340, which increases the availability of oxygen radicals forconformal radical oxidation leading to an increased growth rate of theconformal oxide film. While activated argon can be deactivated byreaction with other species in the high aspect ratio feature 340,activated argon is not further consumed by attachment to the surfaces ofthe high aspect ratio feature 340. As a result, more activated argon canpenetrate to the bottom of the high aspect ratio feature 340 to reactwith, and reactivate, gas phase oxygen, and other species such ashydrogen, that might have been deactivated in transit to the high aspectratio feature 340. The activated argon thus adds chemical potentialenergy to the gas mixture in the high aspect ratio feature 340,increasing overall reactivity, especially at the bottom of the highaspect ratio feature 340.

Although only one high aspect ratio feature 340 is shown in FIG. 3, itshould be understood that the method 200 can be used with substrateshaving multiple high aspect ratio features formed in the film structure300. In some implementations, the film structure 300 may include gatestructures, or precursor structures, for three-dimensional NANDsemiconductor applications. In manufacturing three-dimensional NANDsemiconductor applications, stair-like oxide-nitride pairs of structuresare often utilized to form high aspect ratio gate stack NAND cells toincrease circuit density.

The film structure 300 may be formed on a substrate 302. The filmstructure 300 has a plurality of material layer stacks 306 ₁, 306 ₂, 306₃, 306 ₄ . . . 306 _(n) (collectively 306) formed on the substrate 302sequentially. Each material layer stack of the plurality of materiallayer stacks 306 may include a first film layer 308 ₁, 308 ₂, 308 ₃, 308₄ . . . 308 _(n) (collectively 308) and a second film layer 310 ₁, 310₂, 310 ₃, 310 ₄ . . . 310 _(n) (collectively 310) formed thereon so thatthe film structure 300 includes a plurality of first film layers 308 andsecond film layers 310 formed in alternation. In some implementations,the plurality of first film layers 308 are silicon oxide layers and theplurality of second film layers 310 are silicon nitride layers. Theplurality of material layer stacks 306 may be formed by PECVD depositiontechniques in a plasma-processing chamber.

In further implementations, the first material layer/second materiallayer stacks can be oxide/silicon, silicon/doped silicon, orsilicon/nitride. All of these combinations of materials can be used inBit-Cost Scalable (BiCS), Terabit Cell Array Transistor (TCAT), DRAM,and other 3D memory structures. In other implementations, the firstmaterial layer and second material layer stacks can be othercombinations of materials. The deposition order of the first film layers308 and second film layers 310 on the substrate 302 can also bereversed.

The number of layers can depend upon the memory device being fabricated.In some implementations, the stack numbers could be 8×, or 16×, or 24×,or even higher, where each stack of 8, 16, 24, 32, 64, 128 or morelayers corresponds to one memory device. The two layers of differentmaterials form each stack, so the corresponding number of layers for an8× stack number can be 16, a 16× stack number can have 32 layers, a 24×stack number can have 48 layers, and a higher stack number can have arespectively higher number of layers.

In some implementations, the substrate 302 may have a substantiallyplanar surface, an uneven surface, or a substantially planar surfacehaving a structure formed thereon. The substrate 302 may be a materialsuch as crystalline silicon (e.g., Si<100> or Si<111>), silicon oxide,strained silicon, silicon germanium, doped or undoped polysilicon, dopedor undoped silicon wafers and patterned or non-patterned wafers siliconon insulator (SOI), carbon doped silicon oxides, silicon nitride, dopedsilicon, germanium, gallium arsenide, glass, sapphire. The substrate 302may have various shapes and dimensions, such as 200 mm or 300 mmdiameter wafers and rectangular or square panels. Unless otherwisenoted, implementations and examples described herein refer to substrateshaving a 300 mm diameter. In some implementations, the substrate 302 maybe a crystalline silicon substrate (e.g., monocrystalline silicon orpolycrystalline silicon).

The high aspect ratio feature 340 has an opening 350. The high aspectratio is defined by a bottom surface 360 and a sidewall 370. In someimplementations, the bottom surface 360 is an exposed silicon orsilicon-containing surface (e.g., monocrystalline silicon surface). Insome implementations, the bottom surface 360 is an exposed germanium orgermanium-containing surface. In some implementations, the bottomsurface 360 is defined by an exposed surface of the substrate 302. Insome implementations where the high aspect ratio feature 340 does notextend to the surface of the substrate 302, the bottom surface 360 maybe defined by the material layer stacks 306 or a base layer, if present.The sidewall 370 is defined by the plurality of material layer stacks306.

The methods described herein improve conformality of layers formed inthe high aspect ratio feature 340 at aspect ratios (the ratio of theheight of the bare hole divided by the width of the hole) of at leastabout 5:1 or more (e.g., an aspect ratio of 6:1 or more, 7:1 or more,8:1 or more, 9:1 or more, 10:1 or more, 11:1 or more, 12:1 or more, 20:1or more, 50:1 or more, 100:1 or more, 16:7 or more, or about 10:1 toabout 20:1, or in the range of about 30:1 to about 50:1; or in the rangeof about 40:1 to about 100:1; or in the range of about 70:1 to about100:1). Examples of feature definitions include channels, vias,trenches, gaps, lines, contact-holes, through-holes or other featuredefinitions utilized in a semiconductor, solar, or other electronicdevices, such as high ratio contact plugs.

In some implementations, the substrate 302 is positioned in theprocessing region 113 under a non-reactive atmosphere and subjected to atemperature and pressure ramp-up process. Gases that are considerednon-reactive include, but are not limited to, nitrogen gas (N₂), helium(He), argon (Ar), neon (Ne), and xenon (Xe). The hydrogen, argon, and/oroxygen containing gases may be fed into the processing region 113 priorto and/or during the ramping-up of temperature and pressure. Thehydrogen, argon, and/or oxygen containing gases can be introduceddirectly into the processing region 113. In some implementations, thehydrogen, argon, and/or oxygen containing gases can be introduced intothe processing region 113 via the precursor activator 180. In someimplementations, the non-reactive atmosphere may be maintained duringthe ramp-up by flowing non-reactive gas into and out of the processchamber. Temperature and pressure may be ramped in any pattern,simultaneously or consecutively, up to the targeted predeterminedprocess conditions.

In some implementations, the methods described herein are performed bymaintaining a pressure in the processing region 113 less than 20 Torr,for example, between about 1 Torr to about 10 Torr (e.g., between about2 Torr and about 8 Torr; between about 2 Torr and about 3 Torr, orbetween about 2.5 Torr and about 3 Torr). In some implementations, themethods described herein are performed by maintaining a substratetemperature between about 500 degrees Celsius and about 1100 degreesCelsius, for example, between about 600 degrees Celsius to about 1100degrees Celsius; between about 700 degrees Celsius to about 800 degreesCelsius; or between about 750 degrees Celsius to about 800 degreesCelsius.

In some implementations, during processing, the chamber, the substrate,or both is maintained at a temperature between about 700 degrees Celsiusto about 800 degrees Celsius and a chamber pressure between about 2 Torrand about 3 Torr.

At operation 220, the method 200 can further include flowing hydrogengas into the processing region 113. In some implementations, thehydrogen gas is introduced directly into the processing region 113. Insome implementations, the hydrogen gas is introduced into the processingregion 113 via the precursor activator 180. In some implementations,hydrogen gas is introduced into the processing region 113 both directlyand via the precursor activator 180. Hydrogen gas may be fed to theprocess chamber during the ramping-up of temperature and pressure orflowed after a set temperature is reached for better process control. Insome implementations, the set temperature includes the substratetemperatures described above. Although hydrogen (H₂) gas is used, othergases, such as ammonia (NH₃) may be used.

For a 300 mm substrate in an appropriately sized chamber, the flow ratesof H₂ can be from about 0.01 slm to about 20 slm (e.g., from about 1 slmto about 10 slm) for a 300 millimeter substrate. The hydrogen can beflowed into the chamber to maintain an overall chamber pressure of about0.01 Torr to about 10 Torr (e.g., between about 0.5 Torr and about 8Torr; between about 0.5 Torr and about 5 Torr; between about 2 Torr andabout 3 Torr; or between about 2.5 Torr and about 3 Torr). In someimplementations, the temperature of the substrate can be ramped tobetween about 500 degrees Celsius and about 1100 degrees Celsius, suchas about 800 degrees Celsius.

In some implementations, at least one of oxygen and argon is introducedinto the processing region 113 prior to generating plasma from theplasma precursor gas mixture at operation 230. The oxygen and/or argoncan be introduced directly into the processing region 113. Alternately,the oxygen and/or argon can be introduced into the processing region 113via the precursor activator 180. In some implementations, the oxygenand/or argon is introduced into the processing region 113 for a durationbetween about 5 seconds and about 30 seconds, for example about 15seconds for a 300 mm substrate. The flowing of the oxygen and/or argongas mixture prior to the introduction of the plasma species is believedto provide continuous thermal and pressure stabilization of theprocessing region 113. The stabilization process may be performed priorto operation 230, or may overlap with the operation 230.

At operation 230, the method 200 further includes generating a remoteplasma from a plasma precursor gas mixture comprising at least oxygengas, argon gas and optionally hydrogen gas. Although oxygen (O₂) gas isused, other gases, such as nitrous oxide (N₂O) may be used. In someimplementations, the flow rate of the oxygen gas, the argon gas, andoptionally hydrogen gas are ramped up to a set point to allowtemperature, pressure, and flow controls to respond as the reactionbegins. Not to be bound by theory, it is believed that inclusion ofhydrogen in the plasma precursor gas mixture further improves theconformality of oxidation in HAR structures as well as increasing thegrowth rate of the oxide film. In some implementations, the remoteplasma is generated in the precursor activator 180. Oxygen is suppliedto the precursor activator 180 by the first gas source 192, argon gas issupplied to the precursor activator 180 by the second gas source 198,and hydrogen gas is supplied to the precursor activator 180 by the thirdgas source 199.

In operation 230, the oxygen gas is flowed into the precursor activator180 at from about 0.01 slm to about 15 slm for a 300 millimetersubstrate (e.g., from about 1 slm to about 10 slm for a 300 millimetersubstrate). The oxygen gas can be mixed with argon gas and hydrogen gasto form the plasma precursor gas mixture. In some implementations, argongas is flowed into the precursor activator 180 at from about 0.01 slm toabout 15 slm for a 300 millimeter substrate (e.g., from about 1 slm toabout 10 slm for a 300 millimeter substrate). In some implementations,hydrogen gas is flowed into the precursor activator 180 at from about0.01 slm to about 20 slm (e.g., from about 1 slm to about 10 slm for a300 millimeter substrate). In some implementations, the plasma precursorgas mixture includes an additional inert gas. The additional inert gascan include gases such as helium or krypton. The plasma precursor gasmixture can then be converted to plasma using an energy source. Theenergy source can be a RPS, magnetron typed plasma source, a ModifiedMagnetron Typed (MMT) plasma source, a remote plasma oxidation (RPO)source, a capcitively coupled plasma (CCP) source, an inductivelycoupled plasma (ICP) source, a microwave source, an ultravioletradiation source, or a toroidal plasma source.

In some implementations where hydrogen is not included in the plasma,but is provided directly to the processing region 113, the plasmaprecursor gas mixture includes oxygen (O₂) and argon (Ar), and aconcentration of argon up to about 55 percent provides a beneficialeffect on film growth rate and conformality. Above about 55 percent, thebeneficial effect may be realized to a lesser extent. The argonconcentration, relative to the total of oxygen and argon, is at least0.5 percent up to 55 percent, such as 20 percent to 50 percent, or 30percent to 40 percent, for example 35 percent. In such cases, aconcentration of oxygen in the plasma precursor gas is at least 19.5percent up to 95.5 percent, such as 45 percent up to 95.5 percent, suchas 50 percent to 80 percent, or 60 percent to 70 percent, for example 65percent.

In some implementations, where the plasma precursor gas mixture includesoxygen (O₂), argon (Ar), and hydrogen (H₂), argon concentration,relative to the total of oxygen, argon, and hydrogen, is at least 0.5percent up to 80 percent, such as 20 percent to 50 percent, or 30percent to 40 percent, for example 35 percent. In such cases, aconcentration of oxygen in the plasma precursor gas is at least 20percent up to 95.5 percent, such as 45.5% to 90%, or 50 percent to 80percent, or 60 percent to 70 percent, for example 60 percent. Also insuch cases, hydrogen concentration, relative to the total of oxygen,argon, and hydrogen, is at least 0.5 percent up to 80 percent, such as 5percent to 50 percent, or 10 percent to 40 percent, or 20 percent, to 30percent, for example 5 percent.

In some implementations, the oxygen concentration (O₂/(H₂+O₂)%) is about20 percent or more.

The plasma precursor gas mixture is provided at total flow rate ofbetween about 1,000 sccm and 50,000 sccm (e.g., between about 6,000 sccmand about 15,000 sccm; or between about 10,000 sccm and about 35,000sccm; or between about 25,000 sccm and about 35,000 sccm) in thepercentage ranges described above. For example, when both oxygen (O₂)and argon (Ar) are provided, the oxygen (O₂) and argon (Ar) is providedin a total flow rate of between about 10,000 sccm and about 50,000 sccm,especially between about 25,000 sccm and about 35,000 sccm, or at about30,000 sccm, in the percentage ranges described above. Where the plasmaforming gas includes oxygen (O₂), argon (Ar), and hydrogen (H₂), oxygen(O₂), argon (Ar), and hydrogen (H₂) are provided at a total flow rate ofbetween about 10,000 sccm and about 50,000 sccm (e.g., between about10,000 sccm and about 35,000 sccm; or between about 25,000 sccm andabout 35,000 sccm) in the percentage ranges described above.

Gas flows for the operations described herein can be controlled byratio. Ratio of argon to oxygen in the gas mixture affects theconformality and growth rate of layers formed in the processes describedherein, and different ratios may achieve the most beneficial results indifferent processes. For the processes described herein, the gas flowratio of oxygen gas to argon gas (O₂:Ar) is between 1:4 and 50:1 (e.g.,1:1 to 20:1; 1:1 to 5:1; or 5:1 to 10:1) is used.

Using the substrate processing system 100 of FIG. 1, the plasmaprecursor gas mixture is activated by exposure to RF power. Exposure toRF power ionizes at least a portion of the plasma precursor gas mixture,forming a plasma. RF power at a frequency between about 10 kHz and about14 MHz is applied at a power level between about 1,000 W and about 5,000W (e.g., between about 2,000 W and about 3,000 W, or about 2,500 W) tocreate the plasma. In one example, a frequency of 13.56 MHz is used. Inanother example, a lower frequency of 400 kHz is used. Alternately, theoxygen and argon gas mixture may be activated by exposure to a microwavesource, for example a 2.45 GHz microwave source. The microwave sourcecan be operated at a power level between about 1,000 W and 5,000 Watts,for example, 3,000 Watts depending on the gas flow rate through themicrowave source and the degree of activation.

At operation 240, the method 200 further includes flowing the remoteplasma into the processing chamber. In some implementations wherehydrogen gas is present in the processing region 113, the remote plasmamixes with the hydrogen gas to create an activated processing gas. Theplasma is mixed with the hydrogen over the substrate, creating H, O andOH species. In some implementations, where hydrogen is part of theplasma precursor gas, the remote plasma serves as the activatedprocessing gas. When using plasma, residence time of the plasma in theinterior space 184 and the delivery line 190, and activation extent canbe selected to provide a targeted amount of quenching before the plasmareaches the processing region 113. As gas residence time increases at agiven level of activation, higher plasma quenching is realized, and aless active gas is provided to the processing region 113. Similarly, asgas residence time decreases, less quenching is realized.

In some implementations, the chamber is purged with an inert gas orhydrogen gas prior to forming the activated gas. The purge can occursimultaneously with the formation of the oxygen and argon plasma. Aswell, the hydrogen may be flowed into the chamber before the oxygen andargon plasma is flowed from the remote plasma source or flowedsimultaneously to mix with the oxygen and argon plasma over thesubstrate.

At operation 250, the method 200 further includes exposing the substrateto activated gas to oxidize the substrate surface to form an oxide film,such as silicon oxide layer 380 as shown in FIG. 3B. In someimplementations, the silicon oxide layer is a conformal silicon oxidelayer.

At operation, 260, the flow rate of argon is controlled to eitherincrease or decrease the oxide deposition rate. It has been found by theinventors that flowing argon into either a remote plasma source orchamber slit valve generates high-energy argon species and thesehigh-energy argon species prevent the recombination of oxygen radicals.Thus, the growth rate of the oxide film can be increased by increasingthe flow of argon gas into the remote plasma source, which reducesoxygen radical recombination and provides increased oxygen radicalconcentration for oxide formation. Additionally, in some implementationswhere it is appropriate to reduce the growth rate of the oxide film,decreasing the flow of argon gas into the remote plasma source increasesoxygen radical recombination, which despite increasing concentration ofoxygen species, reduces the amount of oxygen radicals available foroxide film growth leading to a decreased growth rate. Thus, argonprovides an independent knob of either increasing or decreasing oxidefilm growth rate for remote plasma oxidation processes. In addition, Araddition can tune within wafer uniformity of oxidation independentlyfrom other parameters (pressure, flow, temperature, etc).

FIG. 4 is a graph 400 depicting growth rate and center to edgeuniformity of an oxide film formed according to implementationsdescribed herein. As depicted in FIG. 4, growth rate starts to decreasebeyond 50% argon in the remote plasma. As further depicted in FIG. 4,the oxide growth rate with argon of approximately 15% is about 3%greater than oxide film grown without argon, for H₂/(H₂+O₂) of 10%,despite apparent dilution of reaction precursor gases in the processingchamber when using argon. Not to be bound by theory, it appears thatdeactivation of activated species increases faster than overallconcentration of reaction species (as opposed to non-reaction speciessuch as argon) as argon concentration decreases, leading to an overallreduction in film growth rate as argon concentration decreases. Thus,film growth rate, in the methods described herein, has an inverserelation to argon flow rate, up to about 55 percent argon based on totalargon plus oxygen species, all other conditions being equal. Beyondabout 55 percent, a lesser benefit is realized. Additionally,conformality of the deposited film has a direct relationship to argonflow rate, since more argon reduces concentration gradient of activespecies in HAR features such as the high aspect ratio feature 340.

FIG. 5 is a graph 500 depicting oxide conformality based on the percentof hydrogen gas and the presence or absence of argon. The portion ofgraph 500, which is labeled “No”, was performed with hydrogen gas andoxygen gas only. The portion of the graph 500, which is labeled “Yes”,was performed with hydrogen gas, oxygen gas, and argon gas. As depictedin graph 500, only certain percentages of hydrogen gas in the presenceof argon will yield an improvement in conformality of the as-depositedoxide film.

FIG. 6 is a graph 600 depicting oxide quality based on the percent ofhydrogen gas relative to the percent of argon gas. The graph 600demonstrates that without argon, certain percentages of hydrogen gas candegrade oxide quality. Sufficient addition of argon gas can eithereliminate or reduce the reduction in oxide quality that is presentwithout argon gas.

In summary, some implementations described herein enable the growth ofconformal oxide films (e.g., silicon oxides) within HAR structures. Ithas been found by the inventors that argon addition during someimplementations of remote plasma oxidation can improve conformaloxidation growth while improving pattern loading. Not to be bound bytheory but it is believed that the addition of argon gas reduces therecombination of oxygen radicals, which increases the concentration ofoxygen radicals available for the plasma oxidation process. Thus, argongas can be used to control the growth rate of an oxide film. Forexample, an increase in the flow of argon gas will typically yield anincrease in the growth rate of the oxide film, whereas a decrease in theflow of argon gas will typically yield a decrease in the growth rate ofthe oxide film.

When introducing elements of the present disclosure or exemplary aspectsor implementation(s) thereof, the articles “a,” “an,” “the” and “said”are intended to mean that there are one or more of the elements.

The terms “comprising,” “including” and “having” are intended to beinclusive and mean that there may be additional elements other than thelisted elements.

While the foregoing is directed to implementations of the presentdisclosure, other and further implementations of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A method for oxidation, comprising: positioning a substrate in aprocessing region of a processing chamber; flowing hydrogen gas into aprecursor activator at a first flow rate, wherein the precursoractivator is fluidly coupled with the processing region; flowing oxygengas into the precursor activator at a second flow rate; flowing argongas into the precursor activator at a third flow rate; generating aplasma in the precursor activator from the hydrogen gas, the oxygen gas,and the argon gas; flowing the plasma into the processing region; andexposing the substrate to the plasma to form an oxide film on thesubstrate, wherein a growth rate of the oxide film is controlled byadjusting the third flow rate.
 2. The method of claim 1, furthercomprising increasing the third flow rate to increase the growth rate ofthe oxide film.
 3. The method of claim 1, further comprising decreasingthe third flow rate to decrease the growth rate of the oxide film. 4.The method of claim 1, wherein a ratio of the second flow rate to thethird flow rate (O₂:Ar) is between about 1:1 and about 5:1.
 5. Themethod of claim 1, further comprising flowing the hydrogen gas throughthe precursor activator and into the processing region prior togenerating the plasma.
 6. The method of claim 1, further comprisingflowing the oxygen gas and/or the argon gas into the processing regionprior to flowing the plasma into the processing region.
 7. The method ofclaim 1, wherein a concentration of the argon gas in the precursoractivator, based on a total amount of the argon gas, the oxygen gas, andthe hydrogen gas, is between 20 percent and 50 percent.
 8. The method ofclaim 1, wherein the substrate comprises at least one of an exposedsilicon nitride surface, an exposed polysilicon surface, an exposedalumina surface, an exposed crystalline silicon surface, and an exposedsilicon oxide surface.
 9. The method of claim 1, wherein the substrateis maintained at a temperature between 500 degrees Celsius and 1100degrees Celsius.
 10. The method of claim 9, wherein the processingregion is maintained at a pressure between about 0.5 Torr and about 5Torr.
 11. A method for oxidation, comprising: positioning a substrate ina processing region of a processing chamber; flowing hydrogen gas into aprecursor activator at a first flow rate, wherein the precursoractivator is fluidly coupled with the processing region; flowing oxygengas into the precursor activator and into the processing region at asecond flow rate; flowing argon gas into the precursor activator andinto the processing region at a third flow rate; generating a plasma inthe precursor activator from the hydrogen gas, the oxygen gas, and theargon gas; flowing the plasma into the processing region; and exposingthe substrate to the plasma to form an oxide film on the substrate,wherein a growth rate of the oxide film is controlled by adjusting thethird flow rate.
 12. The method of claim 11, wherein the substrate ismaintained at a temperature between 500 degrees Celsius and 1100 degreesCelsius.
 13. The method of claim 12, wherein the processing region ismaintained at a pressure between about 0.5 Torr and about 5 Torr. 14.The method of claim 13, wherein a concentration of the argon gas in theprecursor activator, based on a total amount of the argon gas, theoxygen gas, and the hydrogen gas, is between 20 percent and 50 percent.15. The method of claim 14, wherein the substrate comprises at least oneof an exposed silicon nitride surface, an exposed polysilicon surface,an exposed alumina surface, an exposed crystalline silicon surface, andan exposed silicon oxide surface.
 16. A method for oxidation,comprising: positioning a substrate having a high aspect ratio featureformed thereon in a processing region of a processing chamber, whereinthe high aspect ratio feature has an aspect ratio of 40:1 or greater;flowing hydrogen gas into a precursor activator at a first flow rate,wherein the precursor activator is fluidly coupled with the processingregion; flowing oxygen gas into the precursor activator at a second flowrate; flowing argon gas into the precursor activator at a third flowrate; generating a plasma in the precursor activator from the hydrogengas, the oxygen gas, and the argon gas; flowing the plasma into theprocessing region; and exposing the substrate to the plasma to form anoxide film on faces that define the high aspect ratio feature, wherein agrowth rate of the oxide film is controlled by adjusting the third flowrate.
 17. The method of claim 16, further comprising increasing thethird flow rate to increase the growth rate of the oxide film.
 18. Themethod of claim 16, further comprising decreasing the third flow rate todecrease the growth rate of the oxide film.
 19. The method of claim 16,wherein a concentration of the argon gas in the precursor activator,based on a total amount of the argon gas, the oxygen gas, and thehydrogen gas, is between 20 percent and 50 percent.
 20. The method ofclaim 19, wherein the substrate is maintained at a temperature between700 degrees Celsius and 800 degrees Celsius and at a chamber pressurebetween about 2 Torr and about 3 Torr.